NEW ORLEANS – The 2010 Deepwater Horizon oil spill significantly altered microbial communities thriving near shipwrecks in the Gulf of Mexico, potentially changing these diverse ecosystems and degrading the historically and culturally significant ships they live on, according to new research being presented here. The findings are also revealing how decades-old, or even centuries-old, shipwrecks could be used to monitor the health of deep-ocean ecosystems, and the effects of oil and gas activity in the Gulf, according to the researchers.

There are more than 2,000 known historic shipwrecks sitting on the ocean floor in the Gulf of Mexico, spanning some 500 years of maritime history: from the time of the 16th century Spanish explorers to the American Civil War and through the World War II era. In addition to their historical and cultural significance, historic shipwrecks also serve as artificial reefs, supporting a rich deep-sea ecosystem.

In 2014, a multidisciplinary team of scientists launched a project investigating the effects of the Deepwater Horizon oil spill on shipwrecks that lie hundreds to thousands of feet underwater and the microbial communities forming the base of these ecosystems. The project is the first of its kind to study deep-sea shipwreck microbiomes, and the long-term impacts of an oil spill on shipwrecks and their microbial inhabitants, according to the researchers.

“We are filling a huge void in our scientific understanding of the impacts of the spill,” said Melanie Damour, a marine archaeologist at the Bureau of Ocean Energy Management in New Orleans, Louisiana, and a co-leader of the project.

Leila Hamdan, of George Mason University, and Melanie Damour, of the Bureau of Ocean Energy Management, prepare the ROV before a dive during the Gulf of Mexico Shipwreck Study expedition in July 2014. Hamdan and Damour lead a multi-disciplinary team of scientists examining the effects of Deepwater Horizon spill-related oil and dispersant exposure on deep-water shipwrecks and their microbial communities.Credit: BOEM/Dan Warren, C&C Technologies.

Scientists found that the presence of a shipwreck influences which microbes are present on the seafloor, and the release of 4 million barrels of oil from the Macondo well for 87 days significantly altered nearby shipwreck microbial communities. Even four years after the event, the oil was still affecting the community structure and function of these microbes, potentially impacting other parts of the ecosystem. Laboratory studies found that the dispersant used to clean up the oil spill significantly alters the shipwreck microbial community that forms the foundation for other life, like coral, crabs and fish, which thrive there.

Not only did these studies show that the spill affected these ecosystems, but they also provide a new way to monitor the spill’s effects, said Leila Hamdan, a microbial ecologist at George Mason University in Manassas, Virginia and co-leader of the project.

“The microorganisms in these deep-water habitats, where these artificial reefs are present, they make life habitable, make it luxurious, in a place that is cold and dark and permanently separated from light,” she said. “If we are performing activities in the ocean that potentially change these extremely important communities, we should know about that.”

The laboratory studies also found that oil exposure increases metal corrosion caused by microbes, showing that the oil spill could potentially speed up degradation of the steel-hulled shipwrecks, according to Jennifer Salerno, a microbial ecologist at George Mason University.

A 3D laser scan of the stern section of the German U-boat, U-166, that sunk in the Gulf of Mexico during World War II. The scan shows the U-boat’s conning tower and the build-up of sediments around the hull. Scientists will use this data to document changes at the shipwreck sites, including areas of hull collapse or weakening, and other site-formation processes.Credit: BOEM/C&C Technologies, Inc.

The team also used innovative 3-D laser and sonar technology to obtain high-resolution images of the vessels to document their current state of preservation. In one case, a World War II German U-boat that has been previously examined several times since its discovery in 2001 was found to be buried by more sediment than was observed prior to the spill, although the researchers are working to determine if it was a natural process or related to the oil spill. The team plans to repeatedly scan the shipwrecks to document how they change over time.

“These are pieces of our collective human history down there and they are worth protecting,” said Damour, adding that in some cases these ships may still contain human remains. “We are concerned that the degradation of these sites a lot faster than normal will cause the permanent loss of information that we can never get back.”

Bow of the Ewing Bank Wreck, a 19th century wooden-hulled sailing ship that lies in more than 600 meters (2,000 feet) of water. The image shows a close-up view of the copper sheathing attached to the outside of the wooden hull. After the vessel sank, it became a vibrant artificial reef now colonized by Lophelia pertusa coral (white), Venus flytrap anemones, and many other species of macrofauna.Credit: BOEM/Deep Sea Systems International

Members of the project team will be presenting their new research today at the 2016 Ocean Sciences Meeting co-sponsored by the Association for the Sciences of Limnology and Oceanography, The Oceanography Society and the American Geophysical Union.

The new findings show that deep-sea shipwrecks could be used for long-term monitoring of deep-sea ecosystems, according to the researchers. Understanding this unique ecosystem could aid in protecting and conserving it – both the animals that live on the shipwrecks, and the ships themselves, they said. Information about these shipwrecks could also aid scientists who research the deep sea, and companies performing activities there, the researchers said.

Wood sample collected from the Mardi Gras shipwreck site, which sank some 200 years ago about 56 kilometers (35 miles) off the coast of Louisiana in 1,220 meters (4,000 feet) of water. A wood sample yields important clues about wood species, degradation in the local environment, and potential exposure to hydrocarbons or other contaminants.Credit: BOEM/Melanie Damour

For Hamdan, the experience of working on the shipwreck project has been transformative. “I will never forget the sensation I had when the ROV flew across the dark seafloor, an already beautifully muddy landscape, and suddenly there was a shipwreck, with all of its history and ecology before my eyes,” she said recalling the project’s first expedition in 2014. “It really changed me as a scientist … In a single instant I knew that there was more to the seafloor than I ever really considered.”

Notes for Journalists
The researchers on these studies will present an oral presentation and two poster presentations about their work on Monday, 22 February 2016 at the Ocean Sciences Meeting. The meeting is taking place from 21 – 26 February at the Ernest N. Morial Convention Center in New Orleans. Visit the Ocean Sciences Media Center for information for members of the news media.

The Gulf of Mexico Shipwreck Corrosion, Hydrocarbon Exposure, Microbiology, and Archaeology (GOM-SCHEMA) project is part of the National Oceanographic Partnership Program sponsored by BOEM, the U.S. Naval Research Laboratory, the Bureau of Safety and Environmental Enforcement and George Mason University. More information about the project can be found at: http://hamdanlab.com/GOM-SCHEMA/ and http://www.boem.gov/GOM-SCHEMA/

Abstract:
There are more than 2,000 documented shipwrecks in the Gulf of Mexico. Historic shipwrecks are invaluable cultural resources, but also serve as artificial reefs, enhancing biodiversity in the deep sea. Oil and gas-related activities have the potential to impact shipwreck sites. An estimated 30% of the oil from the Deepwater Horizon spill was deposited in the deep-sea, in areas that contain shipwrecks. We conducted field and laboratory experiments to determine if crude oil, dispersed oil, and/or dispersant affect the community composition, metabolic function, and/or corrosion potential of microorganisms inhabiting shipwrecks. Platforms containing carbon steel coupons (CSC) (n = 34 per platform) were placed at impacted and non-impacted shipwrecks or into four experimental microcosm tanks. After a 2-week acclimation period, tanks were treated with crude oil and/or dispersant or received no treatment. CSC and seawater (SW) samples for bacterial genetic analysis were collected bi-weekly (at 16 wks for field samples). Proteobacteria dominated field and lab CSC bacterial communities (77-97% of sequences). Field CSC bacterial communities differed at each wreck site (P = 0.001), with oil-impacted sites differing from control sites. Lab CSC bacterial communities differed between all treatment groups (P = 0.005) and changed over the course of the experiment (P = 0.001). CSC bacterial species richness, diversity, and dominance increased with time across all treatments indicating the recruitment and establishment of microbial biofilms on CSCs. SW bacterial communities differed between treatment groups (P = 0.001), with the dispersant treatment being most dissimilar from all other treatments (P < 0.01), and changed over time (P = 0.001). Oil- and oil/dispersant-treated CSCs exhibited higher corrosion compared to dispersant and control treatments. These findings indicate that exposure to oil and/or dispersant may alter bacterial community composition and corrosion potential.

Abstract:
Shipwrecks enhance macro-biological diversity in the deep ocean, but, to date, studies have not explored the reef effect on deep-sea microbiological diversity. This is an important concept to address in a restoration framework, as microbial biogeochemical function impacts recruitment and adhesion of higher trophic levels on artificial reefs. In addition, microbial biofilms influence the preservation of shipwrecks through biologically mediated corrosion. Oil and gas-related activities have potential to disrupt the base of the reef trophic web; therefore, bacterial diversity and gene function at six shipwrecks (3 steel-hulled; 3 wood-hulled) in the northern Gulf of Mexico was investigated as part of the GOM-SCHEMA (Shipwreck Corrosion, Hydrocarbon Exposure, Microbiology, and Archaeology) project. Sites were selected based on proximity to the Deepwater Horizon spill’s subsurface plume, depth, hull type, and existing archaeological data. Classification of taxa in sediments adjacent to and at distance from wrecks, in water, and on experimental steel coupons was used to evaluate how the presence of shipwrecks and spill contaminants in the deep biosphere influenced diversity. At all sites, and in all sample types, Proteobacteria were most abundant. Biodiversity was highest in surface sediments and in coupon biofilms adjacent to two steel-hulled wrecks in the study (Halo and Anona) and decreased with sediment depth and distance from the wrecks. Sequences associated with the iron oxidizing Mariprofundus genus were elevated at steel-hulled sites, indicating wreck-specific environmental selection. Despite evidence of the reef effect on microbiomes, bacterial composition was structured primarily by proximity to the spill and secondarily by hull material at all sites. This study provides the first evidence of an artificial reef effect on deep-sea microbial communities and suggests that biodiversity and function of primary colonizers of shipwrecks may be impacted by the spill.

Abstract:
Historic shipwrecks and other archaeological sites are protected by a well-established body of historic preservation laws intended to preserve these sensitive, non-renewable resources. While the cultural, historical, and archaeological value of historic shipwrecks is unequivocal, their function and value as ecosystem monitoring platforms following a major environmental disaster is becoming apparent. Shipwrecks have been found in previous studies to serve as artificial reefs and hotspots of biodiversity, essentially providing the basis for an intact ecosystem. This is especially true in the deepwater marine environment where natural hard-bottom is sparse. Micro- and macro-infaunal diversity on shipwrecks and their sensitivity to environmental change demonstrates the suitability of these platforms for monitoring ecosystem impact and recovery. After the 2010 Deepwater Horizon oil spill, the Bureau of Ocean Energy Management (BOEM) and partners initiated a multidisciplinary study to examine spill effects on shipwrecks and their associated microbial communities. To assess these impacts and to perform comparative analyses, the team collected microbiological, geochemical, and archaeological data at wooden- and metal-hulled shipwrecks within and outside of the subsurface spill-impacted area. Microbial community biodiversity informs us of micro-scale changes while 3D laser and sonar data reveal macro-scale changes. A multidisciplinary approach informs us of the roles microorganisms have in shipwreck degradation and corrosion as well as their response to ecosystem impacts. Results of the study identified multiple lines of evidence that sites were impacted by exposure to spill-related contaminants. Future multidisciplinary studies at these sites, as part of a long-term monitoring program, should inform on ecosystem recovery.